Method making it possible to produce the ideal curvature of a rod of vertebral osteosynthesis material designed to support a patient&#39;s vertebral column

ABSTRACT

A method and system for producing a curvature of a rod of vertebral osteosynthesis material designed to support a vertebral column of a patient is provided. A production unit receives a model defining the curvature of the rod. The curvature of the rod is based on a pre-operative X-ray of the vertical column and defined by a simulated correction to be applied to the lumbar segment to be treated, a deduced curved segment representing the curvature of the rod based at least in part on one or more of a lumbar lordosis or a first curvature above a repositioned apex point and the second curvature below the repositioned apex point, and a translated curved segment representative of the deduced curve segment being translated away from a mean line of the vertebral column. The production unit uses computer aided design to produce the rod.

CROSS-REFERENCE TO RELATED APPLICATION

This application is continuation U.S. application Ser. No. 16/389,348,filed Apr. 19, 2019, which is a continuation of U.S. Serial applicationSer. No. 14/914,474, filed Feb. 25, 2016, now U.S. Pat. No. 10,318,655,which is a national stage entry of PCT/IB2014/064586 filed Sep. 17,2014, under the International Convention claiming priority over FrenchPatent Application No. 1358988 filed Sep. 18, 2013, all of which areincorporated herein by reference in their entirely.

FIELD OF THE INVENTION

The present invention relates to a method making it possible to producethe ideal curvature of a rod of vertebral osteosynthesis materialdesigned to support a patient's vertebral column.

BACKGROUND OF THE INVENTION

It is known to analyze a patient's vertebral column in reference toso-called “pelvic” parameters and different morphotypes of a vertebralcolumn, documented in the scientific literature. The appended FIG. 1very diagrammatically shows the base of the vertebral column, i.e., partof the lumbar vertebrae Land the sacrum S, as well as the femoral headsTF; the aforementioned pelvic criteria are:

-   -   the SS (sacral slope) criterion, which is the incline angle of        the plate of S1 (first vertebra of the sacrum), relative to the        horizontal;    -   the PV (pelvic version) criterion, which is the angle formed by        the straight segment connecting the center of the femoral heads        TF and the center of the plate of S1 with the vertical;    -   the P1 (pelvic incidence) criterion, which is the angle formed        by the straight segment connecting the center of the femoral        heads TF and the center of the plate of S1 with the        perpendicular to the plate of S1.

FIGS. 2A to 2D respectively show:

-   -   a so-called “type 1” morphotype, in which the apex (i.e., the        forwardmost point of the vertebral column) is situated at the        median plane of L5 (fifth lumbar vertebra), and the SS criterion        corresponds to an angle smaller than 35°;    -   a so-called “type 2” morphotype, in which the apex is situated        at the base of L4 (fourth lumbar vertebra), and the SS criterion        corresponds to an angle smaller than 35°;    -   a so-called “type 3” morphotype, in which the apex is situated        at the median plane of L4, and the SS criterion corresponds to        an angle comprised between 35° and 45°.    -   a so-called “type 4” morphotype, in which the apex is situated        at the base of L3 (third lumbar vertebra), and the SS criterion        corresponds to an angle larger than 45°.

It is accepted that an individual will adopt a natural vertebral columnposture, called “economic”, avoiding pain and other pathologies, if hispelvic parameters in particular are in agreement with his backmorphotype. If this is not the case, surgical treatment may beconsidered in order to reestablish proper posture of the vertebralcolumn, in which that agreement exists.

It is well known to perform this type of recovery using rigid vertebralrods, in particular made of metal, fastened to the vertebrae usinganchor members such as pedicle screws or laminar hooks, which rods mustbe curved suitably based on the correction to be done. The publicationof patent application No. WO 98/55038 illustrates material of this type.

It has been shown that imparting the appropriate curvature to a straightrod may be very difficult for a surgeon, the curvature being more orless pronounced in any given location of the rod. Currently, such acurvature is done at the surgeon's discretion and calls greatly on thelatter's experience and dexterity. The trial and error necessary toobtain an appropriate curvature have the significant drawback ofextending the operation time, which is not desirable for the patient,and the risk of implanting a rod with a non-ideal curvature cannot beruled out.

OBJECTS OF THE INVENTION

The present invention aims to resolve this essential drawback.

The patent application publications No. WO 2004/017836 A2, WO2009/254326 A 1 and US 2008/079546 A2 describe methods that do notachieve this goal satisfactorily.

SUMMARY OF THE INVENTION

To that end, the method according to the invention comprises thefollowing steps:

-   -   a) taking a sagittal preoperative x-ray of the vertebral column        of the patient to be treated, extending from the cervical        vertebrae to the femoral heads;    -   b) on that x-ray, identifying: [0020] the so-called “pelvic”        parameters, i.e., the sacral slope, the pelvic version and the        pelvic incidence,        -   the lumbar lordosis,        -   the position of the apical lumbar vertebra, i.e., that            situated furthest forward on the x-ray,        -   at least one of the following measurements:            -   the distance, called SVA, from the vertical of the                posterior upper point of the plate of the first vertebra                of the sacrum, called S1, to the vertical passing                through the center of the 7th cervical vertebra;            -   the distance, called SFD, from the vertical of the                posterior upper point of the plate of S1 to the vertical                passing through the center of the femoral heads;            -   the angle, called T1/SPI, formed between the segment                going from the center of the first dorsal vertebra,                called T1, to the center of the femoral heads and the                vertical to the center of T1, a cloud of points defining                the curvature of the patient's vertebral column,                including one point per vertebral level, positioned at                the center of the upper plate of an affected vertebra,                and a point defining the noted preoperative apex;    -   c) deducing, among predetermined vertebral column morphotypes        and from the noted value of the sacral slope, the morphotype to        which the treated vertebral column corresponds and deducing the        desired postoperative apex point after performing the correction        therefrom, and defining the vertebrae in which the anchor        members for the vertebral rod to be anchored to the vertebrae        will be implanted;    -   d) performing a wire modeling of the patient's vertebral column,        for example using CAD software;    -   e) defining, from said pelvic parameters, a reference centered        at the plate of S 1, the origin point of which is the central        point of that plate;    -   f) positioning the different points of said cloud of points,        attached to each vertebra, in that reference, and drawing arcs        step by step between the identified points, all of the arcs        being tangent to each other and the arc extending from S1 being        tangent to the straight line perpendicular to the plate of S1;    -   g) reading the values of the arc lengths;    -   h) simulating the correction to be applied to the lumbar segment        to be treated as follows:        -   h1) drawing a straight line tangent to the desired            postoperative apex point, moving that straight line to a            vertical position such that the arc attached to that            straight line is tangent to the desired postoperative apex            point, the latter thus being repositioned so as to become            the apex point of the modeled vertebral column segment,        -   h2) defining, as co-radial to each other, the arcs situated            below that apex point and defining as co-radial to each            other the arcs situated above that same apex point, so as to            obtain two different curvatures, one above that apex point            and the other below the apex point,        -   h3) defining the lumbar lordosis as being equal to plus or            minus ten degrees of the pelvic incidence, and defining one            of the following three values as desired:            -   SVA distance smaller than 5 cm;            -   SVA/SFD ratio comprised between −1.9 and +0.1;            -   the value of this ratio is positive on the side of the                vertical of the posterior upper point of the plate of S1                situated toward the femoral heads and is negative on the                side of the vertical situated opposite the femoral                heads;            -   T1/SPI angle comprised between −9° and 0°, that angle                being negative on the side of the vertical at the center                of T1 located toward the femoral heads;        -   h4) defining two arcs concentric to the two curvatures            obtained during step h2 above, which are tangent to each            other at the apex point, those arcs forming a curved segment            representing the ideal curvature of the rod to be implanted            in order to obtain the correction of the vertebral segment            to be treated,        -   h5) translating that curved segment away from the mean line            of the vertebral column, over an evaluated mean distance            going from the center of the vertebrae to the anchor points            of the anchor members for anchoring the rod to the vertebrae            of said vertebral segment to be treated, such that the            position of said curve segment corresponds to the position            the rod will assume once implanted;    -   i) defining the diameter of the rod to be implanted;    -   j) defining a two- or three-dimensional model of the rod, curved        along said curve segment, and    -   k) from a straight rod, producing the curvature of that rod        according to said model.

Preferably, said predetermined vertebral column morphotypes comprise:

-   -   a so-called “type 1” morphotype, in which the apex (i.e., the        forwardmost point of the vertebral column) is situated at the        median plane of L5 (fifth lumbar vertebra), and the SS criterion        corresponds to an angle smaller than 35°;    -   a so-called “type 2” morphotype, in which the apex is situated        at the base of L4 (fourth lumbar vertebra), and the SS criterion        corresponds to an angle smaller than 35°;    -   a so-called “type 3” morphotype, in which the apex is situated        at the median plane of L4, and the SS criterion corresponds to        an angle comprised between 35° and 45°;    -   a so-called “type 4” morphotype, in which the apex is situated        at the base of L3 (third lumbar vertebra), and the SS criterion        corresponds to an angle larger than 45°.

Preferably, the two- or three-dimensional modeling done in step j)consists of establishing a drawing or a plan of the rod to be produced.

Preferably, the curvature produced in step k) is done by cold bending.

Preferably, the method comprises, after step h5) or step i) or step j),the transfer of data relative to the rod to be produced to a serviceprovider responsible for producing the curvature of the rod.

Thus, a practitioner, having determined the shape of the rod to beimplanted using the method according to the invention, transfers thedata relative to the rod to be produced to a service providerresponsible for producing the curvature of the rod. Once that curvatureis produced, the service provider will deliver the curved rod to thepractitioner, who will be able to operate on the patient with hisvertebral rod that is ready to be implanted.

The invention will be well understood, and other features and advantagesthereof will appear, in reference to the appended diagrammatic drawing,showing, as a non-limiting example, different values used to carry outthe method in question and different operations performed in the contextof that implementation.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 very diagrammatically shows the base of the vertebral column;

FIG. 2A shows a so-called “type 1” morphotype, in which the apex issituated at the median plane of L5 and the SS criterion corresponds toan angle smaller than 35°;

FIG. 2B shows a so-called “type 2” morphotype, in which the apex issituated at the base of L4 and the SS criterion corresponds to anglesmaller than 35°;

FIG. 2C shows a so-called “type 3” morphotype, in which the apex issituated at the median plane of L4 and the SS criterion corresponds toangle comprised between 35° and 45°;

FIG. 2D shows a so-called “type 4” morphotype, in which the apex issituated at the base of L3 and the SS criterion corresponds to anglelarger than 45°;

FIG. 3 is a very diagrammatic view of a vertebral column, on which thedefinition points of an SVA value used to implement the method accordingto the invention are shown;

FIG. 4 is a view similar to FIG. 3, which shows the definition points ofthe SVA value and an SFD value, those two values being used to define aratio employed to carry out the method according to the invention;

FIG. 5 is a view similar to FIG. 3, showing the definition points of aso-called T1/SPI value used to carry out the method according to theinvention;

FIGS. 6 to 11 are very diagrammatic views of reference points, segments,arcs of circle and curves used during the different successive steps ofthis method; and

FIG. 12 is, on the left side of that figure, a view of a drawing or planP of the curved vertebral rod to be obtained, the shape of which hasbeen defined by the preceding steps of the method and, on the right sideof that figure, a view of the curved vertebral rod TV, obtained fromthat drawing P.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

FIG. 3 very diagrammatically shows a vertebral column CV, and includesthe following information:

-   -   LL: vertebral segment to be treated;    -   L1, L2, L3, L4, L5, S1, C7: the first, second, third, fourth and        fifth lumbar vertebrae, the first vertebra of the sacrum and the        seventh cervical vertebra, respectively;    -   Apex: the forward most point of the vertebral column; [0064] SS,        PV, Pl: the aforementioned pelvic criteria;    -   TF: the femoral heads, shown by a circle;    -   H1 and V1: the horizontal and vertical, respectively, at the        posterior upper point of the plate of S1;    -   V2: the vertical passing through the center of the 7th cervical        vertebra (C7).

FIG. 4 also mentions a so-called “SFD” value, going from the vertical V1to the vertical passing through the center of the femoral heads TF.

FIG. 5 also mentions a so-called “T1/SPI” value, which is the angleformed between the T1-TF segment going from the center of the firstdorsal vertebra, called T1, to the center of the femoral heads TF andthe vertical V3 to the center of T1.

The various steps of the method are illustrated in FIGS. 6 to 11 asfollows.

FIG. 6: on a sagittal preoperative x-ray of the vertebral column of thepatient to be treated, extending from the cervical vertebrae to thefemoral heads, the following are identified:

-   -   the pelvic parameters,    -   the lumbar lordosis, the position of the apical lumbar vertebra,        i.e., that situated furthest forward on the x-ray,    -   as desired, the SVA distance only, or the SVA distance and the        SFD distance,    -   a cloud of points defining the curvature of the patient's        vertebral column, including one point per vertebral level,        positioned at the center of the upper plate of an affected        vertebra, and a point defining the noted preoperative apex.

The morphotype to which the treated vertebral column corresponds isdeduced on the noted points, among the vertebral column morphotypesshown in FIGS. 2A to 2D, from the value of the noted sacral slope; thedesired postoperative apex point after performing the correction isdeduced therefrom; the vertebrae in which the anchoring members for thevertebral rod to be anchored to the vertebrae will be implanted are alsodefined in this step.

FIGS. 7 and 8: a wire model of the vertebral column of the patient isdone, for example using CAD software;

FIG. 9: a reference centered at the plate of S1 is defined from saidpelvic parameters, the origin point of that reference being the centralpoint of that plate, then the different points of said cloud of points,attached to each vertebra, are positioned in that reference, and arcsbetween the identified points are drawn step by step, all of the arcsbeing tangent to each other and the arc extending from S1 being tangentto the straight line perpendicular to the plate of S1;

FIG. 10: the values of the arc lengths are read, and the correction tobe applied to the lumbar segment to be treated is simulated as follows:

-   -   drawing a straight line tangent to the desired postoperative        apex point, moving that straight line to a vertical position        such that the arc attached to that straight line is tangent to        that desired postoperative apex point, the latter thus being        repositioned so as to become the apex point of the modeled        vertebral column segment,    -   defining, as co-radial to each other, the arcs situated below        that apex point and defining, as co-radial to each other, the        arcs situated above that same apex point, so as to obtain two        different curvatures, one above that apex point and the other        below that apex point,    -   defining the lumbar lordosis as being equal to plus or minus ten        degrees of the pelvic incidence, and defining, as desired, one        of the three following values:        -   SVA distance smaller than 5 cm;        -   SVA/SFD ratio comprised between −1.9 and +0.1; the value of            this ratio is positive on the side of the vertical V1            situated toward the femoral heads TF and is negative on the            side of that vertical V1 situated opposite the femoral heads            TF;        -   T1/SPI angle comprised between −9° and 0 0; this angle is            negative on the side of the vertical V3 at the center of T1            located toward the femoral heads TF;        -   defining two arcs concentric to the two curvatures obtained            in the above step, which are tangent to each other at the            apex point, those arcs forming a curved segment SC            representing the ideal curvature of the rod to be implanted            in order to obtain the correction of the vertebral segment            to be treated.

FIG. 11: the curved segment SC is translated away from the mean line ofthe vertebral column, over an evaluated mean distance going from thecenter of the vertebrae to the anchoring points of the anchoring membersOA (FIG. 10, it is a pedicle screw) for anchoring the rod to thevertebrae of said vertebral segment to be treated, such that theposition of said curve segment SC corresponds to the position that therod will assume once implanted; the diameter of the rod to be implantedbeing defined, a two- or three-dimensional model of that rod is thenestablished, curved along said arcs.

FIG. 12: a drawing or plan P is established from that model, then thevertebral rod TV to be obtained is arranged from that drawing P, inparticular by cold bending.

The method according to the invention thus has the decisive advantage ofmaking it possible to produce the ideal curvature of a rod for vertebralosteosynthesis material designed to support a patient's vertebralcolumn.

What is claimed is:
 1. A method for producing a curvature of a rod ofvertebral osteosynthesis material designed to support a vertebral columnof a patient, the method comprising: receiving, by a production unit, amodel defining the curvature of the rod, the curvature of the rod beingbased on a pre-operative X-ray of the vertical column with a lumbarsegment and representative of: a simulated correction to be applied tothe lumbar segment to be treated, wherein simulated correctioncomprises: a repositioned postoperative apex point and a first curvatureobtained above the repositioned apex point and a second curvatureobtained below the repositioned apex point, and data representative of aredefined lumbar lordosis; a deduced curved segment representing thecurvature of the rod based at least in part on one or more of thedefined lumbar lordosis or the first curvature above the repositionedapex point and the second curvature below the repositioned apex point,and a translated curved segment representative of the deduced curvesegment being translated away from a mean line of the vertebral column;and producing the rod by the production unit using computer aideddesign.
 2. The method of claim 1, further comprising: receiving adiameter of the rod.
 3. The method of claim 1, wherein curved segmentrepresents a desired curvature of the rod to be implanted in order toobtain the correction of the lumbar segment to be treated.
 4. The methodof claim 1, wherein the correction is determined based on at least onemeasurement in the pre-operative X-ray, the at least one measurementcomprises: a SVA distance from a vertical of a posterior upper point ofa plate of a first vertebra of a sacrum (S1) to a vertical passingthrough a center of a seventh cervical vertebra; a SFD distance from thevertical of the posterior upper point of the plate of S1 to a verticalpassing through a center of a femoral head; or a T1/SPI angle formedbetween a segment going from a center of a first dorsal vertebra (T1) tothe center of the femoral head and a vertical line extending from thecenter of T1.
 5. The method of claim 4, wherein the at least onemeasurement is at least one redefined measurement, the at least oneredefined measurement comprises: a SVA distance smaller than 5 cm; aSVA/SFD ratio comprised between −1.9 and +0.1 wherein the ratio ispositive on the side of the vertical of the posterior upper point of theplate of S1 situated toward the femoral heads and is negative on theside of the vertical situated opposite the femoral heads; a T1/SPI anglecomprised between −9° and 0°, that angle being negative on the side ofthe vertical at the center of T1 located toward the femoral heads. 6.The method of claim 1, wherein the postoperative apex point is definedby a vertebral column morphotype comprising one or more of: a type 1morphotype, in which a forwardmost point of the vertebral column issituated at a median plane of L5, and a sacral slope (SS) criterioncorresponds to an angle smaller than 35°; a type 2 morphotype, in whichthe forwardmost point of the vertebral column is situated at a base ofL4, and the SS criterion corresponds to an angle smaller than 35°; atype 3 morphotype, in which the forwardmost point of the vertebralcolumn is situated at a median plane of L4, and the SS criterioncorresponds to an angle between 35° and 45°; or a type 4 morphotype, inwhich the forwardmost point of the vertebral column is situated at abase of L3, and the SS criterion corresponds to an angle larger than45°.
 7. The method of claim 1, wherein the producing includes producingthe curvature of the by cold bending.
 8. The method of claim 1, wherein:the vertebral column extends from the cervical vertebrae to the femoralhead a simulated correction; the curvature of the rod also beingrepresentative of two arcs concentric to the first and second curvaturesobtained, which are tangent to each other at the apex point.
 9. Themethod of claim 1, wherein the model is based on a defined vertebrae inwhich an anchor member for the rod to be anchored to the vertebrae willbe implanted.
 10. The method of claim 1, wherein the data representativeof the redefine lumbar lordosis is equal to plus or minus ten degrees ofa pelvic incidence, the pelvic incidence being represented in thepre-operative X-ray as an angle formed by a straight segment connectinga center of a femoral heads and a center of a plate of sacrum (S1) withthe perpendicular to the plate of S1.
 11. A system for producing acurvature of a rod of vertebral osteosynthesis material designed tosupport a vertebral column of a patient, the system comprising: aproduction unit configured to receive data representative of a modeldefining the curvature of the rod and produce the rod using computeraided design, the curvature of the rod being based on a pre-operativeX-ray of the vertical column with a lumbar segment and the model beingrepresentative of: a simulated correction to be applied to the lumbarsegment to be treated, wherein simulated correction comprises: arepositioned postoperative apex point and a first curvature obtainedabove the repositioned apex point and a second curvature obtained belowthe repositioned apex point, and data representative of lumbar lordosis;a deduced curved segment representing the curvature of the rod based atleast in part on one or more of the defined lumbar lordosis or the firstcurvature above the repositioned apex point and the second curvaturebelow the repositioned apex point, and a translated curved segmentrepresentative of the deduced curve segment being translated away from amean line of the vertebral column.
 12. The system of claim 11, whereinthe rod comprises a diameter.
 13. The system of claim 11, wherein curvedsegment represents a desired curvature of the rod to be implanted inorder to obtain the correction of the lumbar segment to be treated. 14.The system of claim 11, wherein the correction is determined based on atleast one measurement in the pre-operative X-ray, the at least onemeasurement comprises: a SVA distance from a vertical of a posteriorupper point of a plate of a first vertebra of a sacrum (S1) to avertical passing through a center of a seventh cervical vertebra; a SFDdistance from the vertical of the posterior upper point of the plate ofS1 to a vertical passing through a center of a femoral head; or a T1/SPIangle formed between a segment going from a center of a first dorsalvertebra (T1) to the center of the femoral head and a vertical lineextending from the center of T1.
 15. The system of claim 14, wherein theat least one measurement is at least one redefined measurement, the atleast one redefined measurement comprises: a SVA distance smaller than 5cm; a SVA/SFD ratio comprised between −1.9 and +0.1 wherein the ratio ispositive on the side of the vertical of the posterior upper point of theplate of S1 situated toward the femoral heads and is negative on theside of the vertical situated opposite the femoral heads; a T1/SPI anglecomprised between −9° and 0°, that angle being negative on the side ofthe vertical at the center of T1 located toward the femoral heads. 16.The system of claim 11, wherein the postoperative apex point is definedby a vertebral column morphotype comprising one or more of: a type 1morphotype, in which a forwardmost point of the vertebral column issituated at a median plane of L5, and a sacral slope (SS) criterioncorresponds to an angle smaller than 35°; a type 2 morphotype, in whichthe forwardmost point of the vertebral column is situated at a base ofL4, and the SS criterion corresponds to an angle smaller than 35°; atype 3 morphotype, in which the forwardmost point of the vertebralcolumn is situated at a median plane of L4, and the SS criterioncorresponds to an angle between 35° and 45°; or a type 4 morphotype, inwhich the forwardmost point of the vertebral column is situated at abase of L3, and the SS criterion corresponds to an angle larger than45°.
 17. The system of claim 11, wherein the curvature of the rod isproduced by cold bending.
 18. The system of claim 11, wherein thevertebral column extends from the cervical vertebrae to the femoralhead.
 19. The system of claim 11, wherein the model is based on adefined vertebrae in which an anchor member for the rod to be anchoredto the vertebrae will be implanted.
 20. The system of claim 11, whereinthe redefine lumbar lordosis is equal to plus or minus ten degrees of apelvic incidence, the pelvic incidence being represented in thepre-operative X-ray as an angle formed by a straight segment connectinga center of a femoral heads and a center of a plate of sacrum (S1) withthe perpendicular to the plate of S1.